In the manufacture of a semiconductor device, chemical mechanical polishing (generally abbreviated as CMP) is now often used as a polishing technique capable of forming an extremely flat surface. Chemical mechanical polishing is a technique for polishing chemomechanically by letting an aqueous dispersion for chemical mechanical polishing flow down over the surface of a chemical mechanical polishing pad while the chemical mechanical polishing pad and the surface to be polished are brought into slide contact with each other. It is known that the polishing result is greatly affected by the properties and characteristics of the chemical mechanical polishing pad in this chemical mechanical polishing. A wide variety of chemical mechanical polishing pads have been proposed up till now.
For example, JP-A 11-70463 and JP-A 8-216029 propose a chemical mechanical polishing method for carrying out polishing by using polyurethane foam containing fine pores as a chemical mechanical polishing pad and holding an aqueous dispersion for chemical mechanical polishing in pores open to the surface of the pad.
JP-A 8-500622 and JP-A 2000-34416 propose a polishing pad containing a water-soluble polymer dispersed in a water-insoluble matrix resin. This pad is capable of polishing by holding an aqueous dispersion for chemical mechanical polishing in pores formed by the dissolution or elimination of only water-soluble particles which came into contact with the aqueous dispersion for chemical mechanical polishing during chemical mechanical polishing out of water-soluble particles.
Since it is difficult to control the foaming of polyurethane in a desired state in the former pad out of these chemical mechanical polishing pads, the quality of the pad varies and the removal rate and the processing state vary as well. Particularly, a surface defect called “scratch” may be produced on the polished surface and the improvement of the polished surface is desired. Meanwhile, although it is easy to control the size and distribution of pores formed during polishing in the latter pad, in-plane uniformity in the amount of polishing of the polished surface (variations in the amount of polishing at specific points of the polished surface) may become unsatisfactory. Therefore, the improvement of the in-plane uniformity in the amount of polishing is also desired.
Due to growing demand for semiconductor devices having higher integration and a finer design rule, specifications required for the surface state of the polished surface are becoming stricter. Further, a higher removal rate is desired to shorten the process time.
In the above situation, a chemical mechanical polishing pad which gives satisfactory polishing results in terms of the suppression of the production of scratches on the polished surface and in-plane uniformity in the amount of polishing while a high removal rate is maintained is not known yet.